Navigating-protractor.



Patented Ian. 28, I902. C. M. McCUBMICK.

NAVEGATING PBOTBA-CTOR.

(Applicatibn filed Oct. 21. 1901.)

(No Medal.)

TOR

NITE. STATES PATENT OFFICE.

CHARLES M. MCCORMICK, OF THE UNITED STATES NAVY.

NAVIGATING-PROTRAGTOR.

SPECIFICATION forming part of Letters Patent No. 692,060, dated January 28, 1902. Application filed October 21, 1901, Serial No. 79,390. (No model.)

from three relatively-fixed points.

The invention has for an object toprovide a skeleton protractor adapted to rest upon a chart or other surface and having its center within the rings free from all rules, hubs, or arms which obscure the chart or other surface upon which the operator is working.

A further object of the invention is to provide a structure consisting of three concentric rings, two of which have motions in azimuth with regard to thethird,'which is fixed and graduated, while each of the rings is provided with a diametrically-extended cord or wire, which by motion in azimuth can be placed in any designated angle to each other and have a point of common intersection at the center of the space within the rings.

Other and further objects and advantages of the invention will be hereinafter set forth, and the novel features thereof pointed out in the appended claims.

In the drawings, Figure l is a plan view of the protractor, and Fig. 2 a vertical section thereof. Fig. 3 is a detail vertical section through one ofthe securing-blocks for the movable rings. Fig. tis a similar view ata point where thebase projects upward between the movable rings, and Fig. 5 is a detail section showiugthemanner of securing the wires or cords carried by the several rings.

Like letters of reference refer to like parts in the'several figures of the drawings.

. The letter A'designates a base-plate forming a ring or annulus and having centrally thereon a raised portion A, bearing a series of graduations of any desired character-for instance, as shown in Fig. 1,.where they extend for one hundred and eighty degrees to the right and left of a zero-point, thus formfor instance,a cord or wire A -extending across the diameter thereof from the zero-point to the one hundred and eightieth degree gratin ation. Mounted upon this base are two con centric rings movable in azimuth with relation to the portion A and comprising an outer ring B and an inner ring 0, each of which may be held in position by any desired means, although in Fig. 3 a securing-block D is shown, provided with tongues D at opposite sides, adapted to enter the peripheral grooves or ways B and O of the rings B and C, respectively, as shown in Figs. 3 and 4. This block is placed in a cut-away portion of the graduated ring A' and may be secured by a screwfastening D The outer ring B is provided with a diametrically-disposed cord or wire B and an operating'knob B while the inner ring 0 is provided with a similar cord or wire 0 and with an operating-knob C The base A is also adapted to be held in position by means of a handle A? on opposite sides suitably secured to thebase.

In order to bring the diametric wires in as close proximity as possible at their point of intersection so as to accurately determine -the apex of an angle, the wire A is mounted upon the upper surface of the base A and the wire 0 upon the lower surface of the ring 0, while the wire 13 from the outer 'ring Bis carried over the graduated ring A. and inner ring 0 by means of a hanger Bghaving its inner endB deflected downward. to bring the wire into the proper plane.

Under some conditions it is desirable to extend the line of the diametric wires, and this may be accomplished by various means. For instance, an exteusi0narm, E may be provided and secured to the base A by means of an overlapping portion E, through which the threaded handle A may pass. For this purpose an extension A is provided opposite the zero-point of the base, so that the edge E of the arm will lie in line with the wire A while any lateral movement of this arm is prevented by the pins E entering suitable sockets in the extension A. For

too

igating-protractor, but it is adapted for use for numerous other purposes both in drafting and in mathematical calculations. When used for the purpose of locating the exact positionof a vessel upon a chart, the rings are placed over the chart and the angles between three fixed objects are obtained by the use of a sextant inthe usual manner. The rings are then moved to bring the right and left Wires upon the lines of the angles indicated in order to disclose upon the chart the relative position of the ship to the fixed object observed. In this operation theentire instrument will be shifted upon the chart or map to bring the Wires into alinemeut with the representation of the fixed objects thereto, so that the intersection of the wires at once indicates the position of the vessel and leaves unobscured all adjacent portions of the chart.

It will be obvious that changes may be made in the details of construction and configuration Without departing from the spirit of the invention as defined by the appended claims.

Having described my invention and set forth its merits, What I claim, and desire to secure by Letters Patent, is-

1. A protractor comprising a stationary base-ring having an indicating-strand across "its diameter, a plurality of relatively movable concentric rings, and an indicatingstrand carried by and extending across the diameter of each of said movable rings and adapted to cross the strand of the base-ring at its mid-length; substantially as specified.

2-. A protractor comprising a graduated base-ring, a movable concentric ring mounted thereon, and an indicating-strand carried by and extending diametrically across each ring in different horizontal planes to each other; substantially as specified. r

3. A protractor comprising a graduated base-ring, movable concentric rings upon opposite sides of said base-ring, and indicating.

means extending diametrically across each ring; substantially as specific v 4. A protractor comprising a graduated base-ring, movable concentric rings upon opposite sides of said base-ring, indicating means extending diametrically across each ring, and a hanger for said indicating means extending from the outer ring over the inner ring; substantially as specified.

5. A protractor comprising a graduated base-ring, movable concentric rings upon 0pposite sides of said base-ring, indicating means extending diametrically across each ring, and a securing-block having projections to engage each of said movable rings; substantially as specified.

6. A protractor comprising a plurality of relatively movable concentric rings, an indicating-strand extending diametrically across each of said rings, and an extension-arm removably secured to one of said rings; substantially as specified.

7. A protractor comprising a base having a graduated ring thereon, a movable concentric ring mounted upon said base, cords or Wires extending diametrically of each ring, an extension from said base-plate, an extension-arm overlapping said extension, and a securing handle passed through said arm and extension; substantially as specified.

' 8. In a protractor a base-plate having a centrally-disposed graduated ring thereon, an indicating-Wire extending diametrically of said ring, concentric movable rings upon opposite sides of said graduated ring, diametric wires carried by each of said movable rings, and means carried by said graduated ring for holding the movable rings against vertical movement; substantially as specified.

O. In a protractor, a base-plate having a centrally-disposed graduated ring, thereon, an indicating-wire extending diametrically of said ring, concentric movable rings upon opposite sides of said graduated ring, diametric wires carried by each of said movable rings, means carried by said graduated ring for holding the movable rings against vertical movement, and hangers carried by the outer movable ring and extending over the other rings to support the indicating-wire from said outer ring; substantially as specified.

10. A protractor comprising a plurality of relatively movable con-centric rings, indicat ing means extending diametrically of each of said rings, and a separable extension -arm having a contact-face curved upon the radius of the outer face of said rings; substantially as specified. i

In'testimonywhereof I affix my signature in presence of two witnesses.

' CHARLES M. McooRMIoK.

\Vitnesses: I

A. T. SILFVERBERG, CHARLES II. Soo'rr. 

